High hepatic γ-glutamyltransferase (γ-GT) activity with normal serum γ-GT in children with progressive idiopathic cholestasis

γ-Glutamyl transferase (γ-GT) was assayed in the serum and liver hiopsies of children affected with either progressive idiopathic cholestasis (PIC, Byler's disease), or other types of cholestatic (biliary atresia, cholestasis of various origins) and non-cholestatic diseases. The mean liver γ-GT activity was increased significantly only in PIC and biliary atresia. In contrast, the serum γ-GT activity, raised in children with evident damage to the main bile ducts or to the interlobular bile ducts, was normal in children with PIC. Although the mechanism for such a discrepancy between high liver and normal serum γ-GT activties in PIC is still speculative, this peculiarity could prove to be of use in leading to a better understanding of the disease.